Research On Cooperative Path Planning Method Of Multi-medical Distribution Robot Systems

Using mobile robots to replace medical workers enter wards,operating rooms and other hospital areas to complete goods distribution can not only avoid the risk of cross infection of medical workers,but also reduce the heavy workload of medical workers to a certain extent.Especially after the spread of the novel coronavirus pneumonia in early 2020,the demand for medical distribution robots in China and even in the world is becoming more and more urgent.However,for the heavy task demand of the hospital,a single robot can’t complete all distribution requirements.Generally,it often needs multiple robots to cooperatively finish all tasks.Therefore,it is very important to reasonably allocate tasks to robots,plan the robots’ trajectories,and improve the service efficiency.However,the existing path planning technology for multi-medical distribution robot system is not adequate.In this thesis,the path planning technology of multi-medical distribution robot system is investigated in the following aspects:task allocation,path planning and collision avoidance.The main contents are as follows:(1)The modeling of working environment of robots:according to the analysis of the working environment of robots,the characteristics of the robots’movement and the structural characteristics of Petri nets,we propose a general environment modeling method,which lays the foundation for the follow-up research works.(2)Global path planning method for multi-robots with time window in static environments:for a static working environment with certain information,an integer linear programming method is developed to solve the path planning problem of multi-robot system.The proposed method can properly assign distribution tasks to each robot and plan the shortest trajectories from the overall level.Meanwhile,this method also ensurse that all tasks are completed on time at the basis of not exceeding robots’rated capacity.In addition,for the area with limited capacity in the working environment,collisions may occur when multiple robots enter the area at the same time.In view of the above problems,a capacity limit monitor are designed based on Petri net structure,which can effectively prevent robots from entering the capacity limited area at the same time and avoid collision.(3)Real time local path adjust method for multi-robot system in dynamic environments:in view of the environment information is constantly changing in practice,a real-time path planning method based on rolling time domain is developed to ensure all tasks are completed on time.First,robots start to run according to global planned trajectories;Secondly,the working time of robots is divied into several time domains.At the beginning of each time domain,the real-time road traffic condition is fed back through monitor to the central controller of multi-robot system;Thirdly,central controller adjusts robots’trajectories according to changed information,so as to prevent robots fall into a"deadlock" due to sudden congestion and ensure remaining tasks will be completed on time.In addition,according to the real-time feedback of the flow of each area,the central controller judges whether robots will enter congested area at the same time.If above situation exists,central controller will properly design the start-up time of robots in the initial time domain to avoid collision.(4)Simulation verification of real-time path planning method in a hospital environment:the path planning method of multi-medical distribution robot system proposed in this paper is simulated by considering a real hospital environment,and the feasibility and effectiveness of the proposed planning method are verified by analyzing the simulation results.In summary,the global path planning method proposed in this paper effectively improves the security and reliability for multi-medical distribution robots,in order to cooperately performs tasks in actual hospital environments.This way also provides an effective solution to strength the control of the central controller to robots’ trajectories.Then on the base of this way,a real-time local path adjustment method of multiple robots in dynamic environment is further studied,and a research idea is discussed to solve this problem in this paper.